The present invention relates to time delay devices and, more particularly, to a time delay valve disposed in a pneumatic line between an inlet and outlet port and having a moving piston for moving slowly through a first portion of travel by forcing an incompressible metering fluid thtough an orifice and rapidly through a second portion by dumping the metering fluid around the piston to rapidly expose the outlet port to the pressurized gas at the end of the time delay period.
Electronic and optical countermeasure devices and the like are carried by many aircraft flying through hostile environments. The devices are carried within launch tubes on the aircraft and include thermal batteries for powering the electronics contained therein. Upon the detection of an approaching hostile missile, the device is launched to decoy the missile away from the aircraft. To activate and eject the device, an explosive squib is typically ignited causing a charge of pressurized gas to be created within the launch tube. The pressurized gas serves two functions. First, it depresses a firing pin to start the pyrotechnic battery contained within the device. This causes the battery to begin electrical operation to power the electronics. Secondly, it creates a pushing force on the device to launch it from the tube. Typically, the battery is divided into two portions; a main portion which powers the electronics for the majority of their limited operational life and a second, rapid start up section, which comes up to operating potential very rapidly so as to have the electronics operational at the time that the ejection of the device from the tube occurs.
While the foregoing battery and ejection arrangement works successfully for its intended purpose, it is not without its drawbacks. First, the rapid start up battery section is very costly. Second, the rapid start up battery section is large and, therefore, occupies space that could be put to better use in improving the performance and capability of the countermeasure device. The time for the main battery to reach its operating potential is small but sufficient to create operating difficulties if a rapid start up section is not employed in conventional launch systems. If a slight delay could be effected between the time that the firing pin is depressed and the device is launched from the tube, the rapid start up battery section could be eliminated with attendant benefits.
Wherefore, it is the object of the present invention to provide a means for effecting such a time delay in the launch systems of such electronic countermeasure devices.
It is a further object of the present invention to effect such a time delay in a manner which requires minimum changes to the aircraft launch system and no changes to the electronic countermeasure devices presently in use, such that benefits but no waste will be created by the availability of the present invention.